What was the doctrine of baptisms in Heb 6:2?

[tonychanyt]

Jesus began his Sermon on the Mount in Mt 5 and ended it in (ESV) 7:

28 And when Jesus finished these sayings, the crowds were astonished at his teaching,

teaching,
διδαχῇ (didachē)
Noun - Dative Feminine Singular Strong's 1322
Strong's Greek: 1322. διδαχή (didaché) — 30 Occurrences

NASB Translation:
instruction (2), teaching (27), teachings (1).

29 for he was teaching them as one who had authority, and not as their scribes.

was teaching
διδάσκων (didaskōn)
Verb - Present Participle Active - Nominative Masculine Singular
Strong's 1321

NKJV:

28 And so it was, when Jesus had ended these sayings, that the people were astonished at His teaching, 29 for He taught them as one having authority, and not as the scribes.

The same lexeme G1322 appeared in (NKJV) Heb 6:

1 Therefore, leaving the discussion of the elementary principles of Christ, let us go on to perfection, not laying again the foundation of repentance from dead works and of faith toward God, 2 of the doctrine of baptisms, of laying on of hands, of resurrection of the dead, and of eternal judgment.

On this occasion, NKJV decided to translate G1322 as "doctrine".

BDAG:
① the activity of teaching, teaching, instruction ② the content of teaching

I think NKJV overstated G1322 in Heb 6:2. Berean Literal Bible:

instruction about baptisms, and of laying on of hands, and of the resurrection of the dead, and of eternal judgment.

Moreover:
about baptisms,
βαπτισμῶν (baptismōn)
Noun - Genitive Masculine Plural
Strong's 909: Dipping, washing (of a ceremonial character). From baptizo; ablution.
Strong's Greek: 909. βαπτισμός (baptismos) — 5 Occurrences

G909 appeared only 5 times in the NT.

Mark 7:

4 and when they come from the marketplace, they do not eat unless they wash.

they wash.
βαπτίσωνται (baptisōntai)
Verb - Aorist Subjunctive Middle - 3rd Person Plural Strong's 907

And there are many other traditions that they observe, such as the washing of cups and pots and copper vessels and dining couches.)

the washing
βαπτισμοὺς (baptismous)
Noun - Accusative Masculine Plural
Strong's 909

Now back to NKJV, Heb 6:

2 of the doctrine of baptisms, of laying on of hands, of resurrection of the dead, and of eternal judgment.

English Standard Version:

and of instruction about washings, the laying on of hands, the resurrection of the dead, and eternal judgment.

What was the doctrine of baptisms in Heb 6:2?

According to ESV, it was the instruction about washings.